preface to fifteenth edition

GENERAL INFORMATION, CONVERSION TABLES, AND MATHEMATICS 2.111
Perimeter of n-sided regular polygon inscribed in a
circle 2nR sin n
2
Area of inscribed polygon 1⁄2nR2
sin n
Perimeter of n-sided regular polygon circumscribed about a
Area of circumscribed polygon nR2
tan n
circle 2nR tan n
Radius of circle inscribed in a triangle of sides a, b, and c is
(s a)(s b)(s c)
r s 1⁄2(a b c)
s
q
Radius of circle circumscribed about a triangle is
abc
R
4 s(s a)(s b)(s c)
p
Ellipse (Fig. 2.3). A ab, where a and b are lengths of semimajor
and semiminor axes, respectively.
Parabola (Fig. 2.4)
2ld
A 3
d
Height of d (l2 l
2
1 1)
l 2
Widthof l l 1
q
d d 1
d
2 2d
2
2 2d
4
Lengthof arc l 1 ···
3 l 5 l
Area by Approximation (Fig. 2.5). If y 0 , y 1 , y 2 ,..., y n arethelengthof a series of equally
spaced parallel chords, and if h is their distance apart, the area enclosed by the boundary is given
approximately by any one of the following formulae:
A h[ 1
T ⁄2(y0 y n) y1 y2 ··· y n1] (Trapezoidal Rule)
FIGURE 2.3
FIGURE 2.4
FIGURE 2.5